1. Field of the Invention
The present invention relates to a transmission signal generating unit and a radar transmission device using the same.
2. Description of Related Art
Since the utilization of radio waves is increasing, narrowing the frequency band of a radar signal is strongly demanded to efficiently use frequencies between various devices.
In addition, suppressing the spurious components of the radar signal as low as possible has become an international issue. The development of technology to narrow the frequency band and to suppress the spurious components enables to operate the radars within a narrower frequency band. This will contribute to solve the shortage of frequencies.
As a solution for these problems, a low-power pulse compression radar is put to practical use.
Japanese Patent Publication Laid-open No. H4-357485 shows a radar signal processing device employing a pulse compression method. This radar signal processing device transmits a chirp signal (liner FM modulated signal) as a transmission signal to a relatively moving target, receives a signal reflected by the moving target as a received signal, then extracts Doppler components due to the movement of the target from the received signal, and detects the moving target based on the Doppler components.
In this pulse compression method, a modulated long pulse is transmitted and after the reception a short pulse is obtained with its signal to noise ratio (SNR) improved by a pulse compression filter suitable for the modulated long pulse. This method has many advantages such as the extension of detection range, the achievement of high range-resolution ability, and the reduction of interference signals. Thus, the method is applied to many radars.